<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="app">

<!--  给input标签一个key值，然后虚拟dom不会复用-->
  <span v-if="isUser">
  <label for="username">用户账号</label>
  <input type="text" id = "username" placeholder="用户账号" key="username">
  </span>
    <span v-else>
  <label for="useremail">用户邮箱</label>
  <input type="text" id="useremail" placeholder="用户邮箱" key="email">
  </span>
    <button @click="isUser = !isUser">切换类型</button>
</div>

<script src="../js/vue.js"></script>
<script>
    const  app = new Vue({
        el:'#app',
        data:{
            message: '卢本伟牛逼！',
            isUser: true
        },
        methods: {

        }
    })
</script>
</body>
</html>